Integration of an integrated gasification combined cycle power plant and coal to liquid facility

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional patent application No. 60/972,450, filed Sep. 14, 2007, and Application No. 60/972,522, filed Sep. 14, 2007, the disclosures of which are incorporated herein by reference in their entirety for all purposes.

BACKGROUND

1. Field of the Invention

This invention relates generally to the field of clean coal energy production. More specifically, the invention relates to a method of combining two clean coal processes into a single facility.

2. Background of the Invention

Natural gas, coal deposits, and biomass are abundant energy sources that often serve as fuel for power generation. The United States has significant known reserves of coal, and coal currently burned for power generation represents only a fraction of the total deposits that are available. This coal used for power satisfies approximately one-half of the electrical energy demand of the United States. Current and tightening emissions regulations limit the amount of sulfur, oxides of nitrogen, and greenhouse gas emissions, making coals high in these materials less favorable for electricity generation. Failure to comply with these regulations results in hefty penalties in the form of fines, shutdowns, and limited operations. Further, upgrading of current coal burning electric generation plants requires substantial investment. With increased awareness of environmental issues such as global warming, and greenhouse gases, this trend is predicted to continue, potentially making coal-burning plants unfavorable and expensive to operate.

Rising worldwide oil demand has increased the cost of oil distillates and encouraged development of alternative clean power facilities. One such power production facility is the Integrated Gasification Combined Cycle (IGCC) plant. Electricity is produced from the combustion of a synthesis gas (syngas) produced by the gasification of coal. Gasification is a method of reacting coal with limited oxygen at high temperatures for the production of synthesis gas. The process of gasification removes potential pollutants such as mercury, arsenic, nitrogen oxides, and sulfur oxides. Further benefits are realized when syngas is combusted, as the burning of syngas releases lower amounts of carbon dioxide. The lowered carbon dioxide emissions and technological advances make these facilities “capture ready,” since stored carbon dioxide from the coal is removed in the gasifier.

Conventional steam turbines require pressure, temperature, and corrosion resistant components to generate electricity. The limitations of these components dictate the upper range of the steam temperatures, and therefore limit efficiency of electric power production. In the case of an IGCC gas turbine, the same limitations do not apply. The gas turbine has a higher gas cycle firing temperature that feeds the compressor, burner, and turbine systems as a means of electricity production. The high-temperature exhaust-gas output of the turbine can be used to heat steam for a supplemental steam turbine, thereby increasing the overall efficiency of an electrical power plant.

Coal may also be converted to a synthetic liquid fuel by the conversion of syngas. Liquid fuels have an advantage over coal in that they are easily transported long distances without expensive processes or packaging. The process of converting coal to a liquid fuel typically involves a catalytic reaction of syngas to form liquid hydrocarbons. Fischer-Tropsch (FT) reactor facilities execute the vital step of catalyzed synthesis of petroleum substitute liquid fuels. The process occurs via a catalyzed chemical reaction in which the carbon monoxide and hydrogen in syngas are converted into liquid hydrocarbons. The production of liquid hydrocarbon fuels from solid material reduces dependence on oil distillates for fuels. The hydrocarbon production reaction is highly exothermic, and requires a cooled reactor to maintain conditions favorable for continued synthesis.

The IGCC and CTL process represent two potential clean coal processes to reduce dependence on oil distillates. The former provides clean electrical power and the latter provides liquid hydrocarbons for further processing into products. Additionally, both processes require coal processing, air separation, and syngas production for operation. The current costs of material, process, capital, and infrastructure make individual investments in these processes expensive rendering them unfavorable for development. Previous discussions on the combination of facilities for these processes have centered on their shared starting material and parallel infrastructure requirements for the production of syngas. However, it is recognized that providing a singular source of syngas to operate a plurality of clean coal plants is disadvantageous for operational flexibility, the capacity to scale output to demand, and maintain production during maintenance, or in the case of a device failure.

Accordingly, there is a need in industry for a method of integrating IGCC and CTL facilities with operational flexibility, scalable output, and online maintenance.

BRIEF SUMMARY

These and other needs in the art are addressed in an embodiment of an integrated Coal to Liquid and Integrated Gasification Combined Cycle facility described herein. A novel method of combining a CTL fuel plant and an IGCC electrical plant by sharing the systems of coal intake, coal preparation, gas separation, and water units is described herein. This configuration allows the combined facility to offer advantages in efficiency of production, operational flexibility, scalability, and reliability by a multi-path integration of the processing units.

In embodiments, coal is received by the plant, and prepared for gasification in handling and preparation units. Additionally, air is separated into oxygen for gasification, and nitrogen for the IGCC gas turbine unit in a shared unit. The prepared coal and gas are routed to the CTL section or the IGCC section of the integrated facility. The direction of the processed materials transportation depends on factors involving the profitability of a given product, the quantity of processed material necessary to produce the product, and the maintenance status of the equipment. The production and purification of synthesis gas, or syngas occurs in the gasification and purification units, which both sections retain. An aspect of the disclosed process is that the produced syngas in one section may be provided to the adjacent section depending upon the profitability of a given product, the quantity of processed material necessary to produce the product, and the maintenance status of the equipment.

Byproduct, waste, or tail gases from the CTL section of the facility may be utilized in the IGCC section as a fuel for the gas turbines. In some cases the syngas feed stream to the CTL is not processed, thereby exiting the reactor for gaseous transportation to the IGCC section. These gases may also be recycled to increase the liquid product from the CTL Fischer-Tropsch reactor unit. Water and wastewater units may be shared between the sections of the facility.

The foregoing has outlined rather broadly the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:

<figref idrefs="DRAWINGS">FIG. 1</figref> illustrates a schematic of non-integrated operations of IGCC and CTL plants;

<figref idrefs="DRAWINGS">FIG. 2</figref> illustrates a process flow diagram according to one embodiment of the method of integrating operations of IGCC and CTL plants;

<figref idrefs="DRAWINGS">FIG. 3</figref> illustrates a detailed process flow diagram according to one embodiment of the method of integrating operations of IGCC and CTL plants;

<figref idrefs="DRAWINGS">FIG. 4</figref> illustrates detailed process flow diagram according to one embodiment of the method of integrating operations of IGCC and CTL plants.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following descriptions and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function.

In the following discussion and in the claims the term “IGCC” is used to refer to an Integrated Gasification Combined Cycle electricity generation plant or facility. Similarly, the term “CTL” or “coal to liquid” is used to refer to a Fischer-Tropsch reactor based plant for the synthesis of liquid hydrocarbons from coal, or coal products without limitation by the individual processes involved. Additionally, the term syngas refers to a gaseous mixture comprised of varying amounts of the main components carbon monoxide and hydrogen with potentially other gaseous molecules.

In further discussion the term “facility”, “section” and “unit” are used in open ended fashion and thus should be interpreted to mean a premises for a system of components for the execution of a step, or series of steps and associated devices, or apparatuses within the described process.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .”

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to <figref idrefs="DRAWINGS">FIG. 1</figref>, that illustrates the components of non-integrated facilities for coal to liquid (CTL) fuel production <b>10</b> and an integrated gasification combined cycle (IGCC) power plant <b>20</b> in a side-by-side manner. CTL facility <b>10</b> comprises a Fischer-Tropsch Reactor <b>47</b> for the production of liquid hydrocarbons. IGCC facility <b>20</b> comprises IGCC gas turbine <b>53</b> for the combustion of syngas to produce electricity. Further, <figref idrefs="DRAWINGS">FIG. 1</figref> illustrates the parallel or similar coal processing steps used in both the facilities. For example without limitation, these may include coal handling <b>31</b>, <b>32</b> coal preparation <b>33</b>, <b>34</b> and gasifier (gasification unit) <b>35</b>, <b>37</b>, and syngas purifier <b>43</b>, <b>45</b>. Additionally, both facilities may comprise a process for gas treatment, water treatment, wastewater treatment, waste removal and/or similar processes understood by one skilled in the art.

In an embodiment, the disclosed process comprises a multi-path means to integrate the CTL <b>10</b> and IGCC <b>20</b> facilities. <figref idrefs="DRAWINGS">FIG. 2</figref> illustrates a novel integrated facility <b>30</b> incorporating an integrated IGCC electrical plant section <b>20</b> and a CTL Fischer Tropsch liquid hydrocarbon production section <b>10</b>. In an embodiment, the coal handling <b>31</b>, and coal preparation <b>33</b> units from the CTL facility <b>10</b> are shared between both sections. Alternatively, it can be envisioned that the coal handling <b>31</b> and coal preparation <b>33</b> units are derived from the IGCC facility <b>20</b> coal handling <b>32</b> and coal preparation <b>34</b> units. Coal delivered to the facility arrives at the coal-handling unit <b>31</b>, before being moved to the coal preparation unit <b>33</b>. The coal is moved between units by conveyors, trucks, slides or other means as known to one skilled in the art.

Determination of which section requires coal for operations is made and the coal is distributed to the CTL gasification unit <b>35</b>, the IGCC gasification unit <b>37</b>, or both. The facility receiving the coal may be considered the receiving facility. Alternatively, the facility without active coal reception may be considered the opposite facility. Coal delivered to the CTL facility <b>10</b> is processed through gasification <b>35</b>, and syngas purification <b>45</b> to feed syngas stream <b>3</b>. Coal delivered to IGCC facility <b>20</b> is processed through gasification <b>37</b> and syngas purification <b>43</b> to feed syngas stream <b>3</b>.

The section of the integrated facility <b>30</b> receiving and processing coal from the coal preparation unit <b>33</b> determines the scale and operations of the opposing side. For instance, the IGCC facility <b>20</b> has a contract to produce a certain amount of electrical power from IGCC gas turbine <b>53</b>. In order to satisfy that contract, IGCC facility <b>20</b> uses at least a portion of the output from coal preparation unit <b>33</b> through IGCC gasifier <b>37</b> and syngas preparation <b>43</b>. CTL facility <b>10</b> and associated CTL gasifier <b>35</b> and syngas purification <b>45</b> only utilize remaining portion of coal. In further embodiments, the receiving facility uses all coal; alternatively a portion thereof. Further, the opposing facility may supplement syngas stream <b>3</b>, which is routed to receiving facility in order to boost production.

In preferred embodiments, syngas stream <b>3</b> is a shared between the CTL facility <b>10</b> and the IGCC facility <b>20</b>. Syngas stream <b>3</b> is routed from either section of the integrated facility <b>30</b> to the other. For instance, syngas stream <b>3</b> is routed from the CTL facility <b>10</b> to the IGCC facility <b>20</b>, and vice versa, without limitation. In an exemplary situation, where maintenance requires the temporary shut down of the IGCC gasifier <b>37</b>, syngas stream <b>3</b> may be routed from the CTL syngas purifier <b>45</b> to the IGCC plant <b>20</b>. In certain embodiments, gasification units <b>35</b>, <b>37</b> and syngas purification <b>43</b>, <b>45</b> may contribute to syngas stream <b>3</b> between the facilities.

Referring now to <figref idrefs="DRAWINGS">FIG. 3</figref>, gases required for the gasification of coal are processed and separated in the Air Separation Unit (hereinafter ASU) <b>39</b> of the integrated facility <b>30</b>. The CTL gasification <b>35</b> and IGCC gasification <b>37</b> units include their own air separation units. Preferably, the CTL gasification <b>35</b> and IGCC gasification <b>37</b> units share a single ASU <b>39</b>. The primary gas required is oxygen, which is distributed to the CTL gasifier <b>35</b>, the IGCC gasifier <b>37</b>, or both for the oxidation of coal and production of syngas. As previously discussed in regards to coal, the rate of delivery, and the facility receiving the oxygen gas determines the scale and operational direction of integrated facility <b>30</b>. The oxygen depleted air, is further separated so as to supply nitrogen to IGCC gas turbine <b>53</b>. ASU <b>39</b> produced gases, such as without limitation, oxygen and nitrogen, are transported inter-facility by enclosed conduits such as without limitation, pipes, tubes, pressurized lines, or tanks. ASU <b>39</b> may utilize any suitable technologies to separate oxygen and nitrogen from air as understood by one skilled in the art. Examples include without limitation, compressors, columns, exchangers, pumps, or combinations thereof.

<figref idrefs="DRAWINGS">FIG. 4</figref> illustrates further potential syngas <b>3</b> and off-gas sharing between the CTL section <b>10</b> and the IGCC section <b>20</b> of the integrated facility <b>30</b>. In embodiments, the off gases, produced by Fischer Tropsch reactors <b>47</b> and the off gases from the refining unit <b>51</b>, can be used to as a co-feed stream <b>5</b> with syngas to the IGCC gas turbine <b>53</b>. As necessary, the Fischer-Tropsch reactors <b>47</b> in the CTL section <b>10</b> may have the reaction temperature reversibly lowered. By lowering the temperature outside of the favorable reaction range, the result is the complete expulsion of syngas input as tail gas into co-feed stream <b>5</b> for feeding to the IGCC turbine <b>53</b>. Without lowering temperature, reactor <b>47</b> creates product stream <b>6</b> for product refining facility <b>51</b>. In certain embodiments, product refining comprises production of diesel, naptha, or other liquid hydrocarbons, without limitation. In further embodiments, the off or tail gases introduced to co-feed stream <b>5</b> may be used as a fuel feed to elevate steam temperature at an associated steam turbine generator <b>49</b>. In alternative embodiments, the off gases from co-feed stream <b>5</b> maybe returned to the reactor <b>47</b> through a tail gas recycling facility <b>59</b>.

Further, the IGCC section <b>20</b> of the integrated facility <b>30</b> may include Fischer Tropsch reactors <b>47</b> inline with the syngas supply stream from the purification unit <b>43</b> to the IGCC turbine <b>53</b>. In this manner, the IGCC section <b>20</b> may produce additional liquid fuels as market demands dictate. The tail gases produced in the reactors may be used to power the IGCC turbine <b>53</b>. In cases where electrical power is immediately required, the temperature of the reactor is sufficiently lowered so that the syngas feed stream exits the reactor as unchanged tail gas. The salient details of this embodiment of the IGCC section <b>20</b> are disclosed in U.S. Pat. No. 6,976,362, incorporated herein by reference in its entirety for all purposes. In certain instances, this arrangement may comprise a bolt-on CTL facility <b>10</b> incorporated into IGCC facility to form an integrated facility <b>30</b>.

Water may be transported through a system of vessels, pipes, valves, and/or pumps, from the water unit to the entirety of the integrated facility <b>30</b>. The water may be supplied to the units of the CTL facility <b>10</b> including the reactor <b>47</b>, the product refining <b>51</b>, the syngas purification <b>43</b> and gasification <b>35</b> units. In further embodiments, water may be provided to a steam turbine <b>49</b> that utilizes heat and steam from the other units to produce quantities of electricity. The other units may comprise any portion of the integrated facility <b>30</b>, that generates suitable thermal waste, or heat for producing steam. Additionally, water may be routed from the gasification unit <b>35</b> to coal preparation unit <b>33</b>. The coal preparation facility <b>33</b> is shared by both CTL <b>10</b> and IGCC <b>20</b> plants. Water supplied to each unit of the CTL section <b>10</b> may be routed through other units in the integrated facility <b>30</b>, disconnected, or removed completely for treatment off premises, without limitations.

Water may also be transported to the IGCC syngas purification unit <b>43</b>, the gas turbine <b>53</b> and the heat recovery steam generator (hereinafter HRSG) <b>55</b>. Steam from HRSG is cycled to steam turbine <b>58</b>. Steam turbine <b>58</b> may produce additional electrical power. In further embodiments, water is provided to the IGCC gasification unit <b>37</b>. The IGCC gasification unit <b>37</b> may further provide water to the coal preparation unit <b>33</b> shared by the CTL <b>10</b> and IGCC <b>20</b> sections. Water supplied to each unit of the IGCC section <b>20</b> may be routed through other units, disconnected or removed completely, as known to one skilled in the art.

A wastewater treatment unit <b>57</b> may be included in the integrated facility <b>30</b>. The wastewater treatment unit <b>57</b> drains the syngas purification units <b>43</b>, <b>45</b>, the gasification units <b>35</b>, <b>37</b>, the CTL reactor <b>47</b>, the CTL product refining facilities <b>51</b>, the coal preparation unit <b>33</b>, and the IGCC gas turbine <b>53</b> of used water. Wastewater removal from individual units of the integrated facility <b>30</b> may be alternatively coupled, routed through other units, or omitted from the system. The wastewater may be recycled, reused, or treated and expelled from the integrated facility.

While embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described and the examples provided herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.